1. Field of the Invention
The present invention relates to a control system for an internal combustion engine that includes a plurality of cylinder banks, and particularly, relates to a control system and a control method for an internal combustion engine that recirculates exhaust gas as EGR gas to an intake passage through an exhaust gas recirculation (EGR) passage.
2. Description of the Related Art
A technique is known that exhaust gas is introduced as EGR gas to an intake passage through an EGR passage that connects an exhaust passage with the intake passage. In this case, an amount of the EGR gas that is introduced to the intake passage through the EGR passage is regulated by controlling a degree of opening of an EGR valve that is provided in the EGR passage. Accordingly, the amount of the EGR gas that is supplied to an internal combustion engine is regulated.
If the EGR valve is stuck in an open state in the above case, an excessive amount of the EGR gas is supplied to the internal combustion engine, and thus affects a combustion state of the internal combustion engine. Consequently, the operation of the internal combustion engine may be destabilized.
Japanese Patent Application Publication No. 2005-207285 (JP-A-2005-207285) describes a technique that when an EGR valve is stuck in an open state, a cylinder cut-off operation is executed to increase an air intake amount per cylinder, thereby lowering an EGR rate. By adopting such a technique to reduce the EGR rate, it is possible to prevent affecting of the combustion state in the internal combustion engine.
However, if the amount of the EGR gas that is introduced to the intake passage is large when the EGR valve is stuck with a large opening degree, it is difficult to sufficiently reduce the EGR rate using the above technique.